Zircon SHRIMP U-Pb ages and geochemistry of Late Mesozoic granitoids in Western Zhejiang and Southern Anhui: constraints on the model of lithospheric thinning of Southeast China

ABSTRACT

We report geochemical data and zircon SHRIMP U-Pb ages for Late Mesozoic granitoids from the western Zhejiang province and southern Anhui province (the WZSA region) from southeast China. In combination with published geochronological and geochemical data, the granitoids in the region can be divided into three stages: 171–141 Ma, 140–121 Ma, and 120–95 Ma. The first stage of these granitoids is mainly composed of granite porphyry and granodiorite which are similar to I-type granitoids, including having weakly negative Eu anomalies with enrichment in light rare earth elements (LREE), Rb, Th, and U. The second stage of granitoids consists of monzogranite, syenogranite, and granite with the characteristics of both A-type and I-type granitoids including strongly negative Eu anomalies; depletion of Ba, Sr, and Ti; and enrichment of K, Rb, and high field strength elements (HFSEs) (such as Th and U). The third stage of granitoids is mainly composed of granite, quartz monzonite, quartz diorite, and mafic rocks with weakly negative Eu anomalies and also enrichment in LREE, Rb, Th, U, and K. From our work, we propose a transition from compressional to extensional magmatism at ~141 Ma. Based on the geochemical characteristics of these granites and coeval mafic rocks, we propose that the formation of the A-type magmatism in the WZSA region formed as the result of lithospheric extension and asthenospheric upwelling during the Early Cretaceous.

KEYWORDS:

• Zircon SHRIMP U-Pb ages
• Early Cretaceous
• tectonic evolution
• lithospheric thinning
• Southeast China

Acknowledgements

Constructive comments by editor Robert J. Stern, guest editors Xiaoyong Yang, Weidong Sun, and three anonymous reviewers significantly improved the paper. We thank members of the Beijing SHRIMP Center for their help with zircon analysis and zircon CL imaging. The first author thanks Linlin Li, Chenyang Hou, and Huiyi Sun for their help in field sampling, and thanks Miss Zhenping  Cao for her encouragement.

This study was financially supported by the Ministry of Land and Resources of Public Welfare Scientific Research (grant number 201311116), the Geological Survey of China (grant numbers 1212011121075, 12120114020901 and 12120115069701), and the Chinese Ministry of Science and Technology (grant number 2012FY120100).

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This study was financially supported by the Ministry of Land and Resources of Public Welfare Scientific Research (grant numbr 201311116), the Geological Survey of China (grant numbers 1212011121075, 12120114020901 and 12120115069701), and the Chinese Ministry of Science and Technology (grant number 2012FY120100).